1. Field of the Invention
The present invention relates to a video or audio recording and reproducing apparatus for multi-layer optical disks.
2. Description of the Related Art
In recent years, shift from tape recording such as VTR recording to disk recording using, for example, DVDs and hard disk drives (HDDs) is being conducted rapidly, because of digitization of images and sounds in the world of video and audio information and improvement of the compression technique for video and audio data. As a representative disk recorder, an HDD&DVD hybrid recorder having a mixture of a hard disk drive (hereafter referred to as HDD) and a DVD drive can be mentioned. This temporarily records video information or audio information supplied from, for example, a broadcasting station or an external input terminal on an HDD, and then records it on a DVD disk in a backup form or the like when preservation is desired. Or the HDD&DVD hybrid recorder records the video information or audio information directly on the DVD disk. In recent years, the HDD&DVD hybrid recorder is sold by various companies, and it is a product growing and forming a large market.
Here, the HDD has a capacity of 80 GB to several hundreds GB. The DVD disk has a capacity of approximately 4.7 GB per disk. As representative DVD disks, there are, for example, digital video disks (hereafter abbreviated to DVD-Video) which are video optical disks for movies or the like, and DVD-ROMs applied to application software, game software and various data recording for computer use. As media for DVD recorders used to conduct backup recording of personal information and to be substituted for VTRs, there are rewritable optical recording media using optical disks such as DVD-RAMs, DVD±RWs and DVD±Rs.
On the other hand, high definition video or audio contents in Hi-Vision broadcasting including digital terrestrial broadcasting are being delivered, and a demand for recording high picture quality or high sound quality information is growing. However, high picture quality or high sound quality information is accordingly high in amount of information. Even if, in the conventional MPEG-2 technique, image data with sound having, for example, image data with sound of the SD quality is recorded at a variable rate of 10 Mbps at maximum, a two-hour program becomes approximately 4.7 GB at maximum in amount of information when the average rate in recording is approximately 5 Mbps. Therefore, it becomes possible to record the two-hour program on one DVD disk having a diameter of 12 cm. In the case of the HD in the digital terrestrial broadcasting, however, the average rate cannot be made less than 15 Mbps in the conventional MPEG-2 because of the balance with the picture quality, even if the compression factor is made large. Therefore, a two-hour program in the HD in the digital terrestrial broadcasting cannot be recorded on a single DVD disk. Even if, for example, the Blu-ray disk is popularized in the near future and optical disk media having a capacity of at least 25 GB per disk are implemented, video contents corresponding to at least two hours and a half cannot be recorded on one disk with a high picture quality mode of, for example, 2 Mbps.
On the other hand, although the HD quality needs 25 Mbps in the conventional MPEG-2, a sufficient HD quality is obtained at approximately 15 Mbps in, for example, H.264 system of MPEG-4 because of a recent advance of the compression technique. In addition, a sufficient HD quality is obtained even at 8 Mbps. At the same time, the SD quality becomes considerably good even at approximately 4 Mbps. It becomes also considerable to record several channels of broadcasting or the same contents having different recording rates at a time, when the digital terrestrial broadcasting has been popularized. A use in which contents with the HD quality and contents with the SD quality are recorded on one disk is also considerable. In this case, for example, a low picture quality is used for delivery and a high picture quality is used for preservation.
In the conventional techniques, there are techniques concerning a method of recording video or audio data of a plurality of channels on an HDD at the same time and techniques concerning a method of recording still picture information in, for example, a digital camera by using two compression systems. As this example, there are JP-A-2002-344892 and JP-A-2001-24929.